Seminars & Colloquia

Microsoft Research

"Limits of Communication"

Consider a function f whose arguments are distributed among several parties, making it impossible for any one party to compute f in isolation. Initiated in 1979, communication complexity theory studies how many bits of communication are needed to evaluate f. I will prove that:

(1) some natural and practical problems require high communication to achieve any advantage at all over random guessing;

(2) solving n instances of any known communication problem on a quantum computer incurs Omega(n) times the cost of a single instance, even to achieve exponentially small correctness probability.

The proofs work by recasting the communication problem geometrically and looking at the dual problem in a novel way. Our results resolve open problems dating back to 1986.

Short Bio:

Alexander Sherstov earned his Ph.D. in Computer Science in August 2009 at the University of Texas at Austin, under the direction of Prof. Adam Klivans, and is currently a postdoctoral researcher at Microsoft Research. He has broad research interests in theoretical computer science, including complexity theory, computational learning theory, and quantum computing.